Sophisticated aircraft generally include a weight on gear switch for activating and deactivating various aircraft systems and flight controls depending upon whether the aircraft is airborne or fully supported by the landing gear on the ground. In some aircraft, such as helicopters, the weight on gear switch also provides an indication to the pilot that the aircraft is either airborne or on the ground.
Aircraft weight on gear switches, or squat switches, are typically actuated by a main landing gear strut when compressed to support the weight of the aircraft. On helicopters with skid landing gear systems, paddles or similar devices have been used to actually contact the ground surface upon landing of the helicopter. However, switches designed to contact the ground are generally unreliable because of collection of dirt and debris or damage from skid movement and objects on the ground. In addition, ground contact switches can give erroneous indications when the helicopter is landing on uneven terrain.
Other types of helicopter weight on gear switches have been based on collective stick position or engine torque. However, these types of switches generally can be overridden by the pilot so that they can indicate the aircraft is airborne when it is actually on the ground.
Another type of weight on gear switch for skid gear helicopters is mounted so as to detect deflection of a cross tube of the skid landing gear. This placement of the weight on gear switch overcomes many of the disadvantages of the ground contact or collective stick position switches. However, switches mounted to indicate deflection of the skid gear cross tube require periodic adjustment as a result of repeated cross tube deflection from normal landings and permanent deformation from harder than normal landings. Without such periodic adjustment, weight on gear switches can give erroneous indications that can affect flight safety.
Therefore, there is a need for a mounting assembly for a helicopter weight on gear switch that is self-adjusting both for normal landing deflection of the skid gear cross tube and for permanent deformation of the cross tube resulting from hard landings.